Metallic lens directive antenna systems



June 28, 1955 w. E. KOCK 2,

METALLIC LENS DIRECTIVE ANTENNA SYSTEMS Original Filed April 8, 1946 2Sheets$heet 1 FIG. 2

- TRANSLATION PM d, DEV/CE FIG. 4 E- PLANE PATTERN fi or HORN F F/G. 3 I

l4 l I i u I u /6 {M 5 i 1 F g I I I 1 l I -20 -/0 -43 0*43 H0 +20 +30DEGREES llvl ENTO/Q M. E. KOCK ATTORNEY June 28,- 1955 w. E. KocK2,712,067

METALLIC mans DIRECTIVE ANTENNA SYSTEMS ori in-a1 Filed April 8,1946 2Sheets-Sheet, 2

TRANSLA T/ON DEV/CE IQ, TRANSLATION DEV/CE 70 lNVE/VTOR W E. KOCK ATTR/VEV Patented June 28, 1955 METALLIC LENS DIRECTIVE ANTENNA SYSTEMSOriginal application April 8, 1946, Serial No. 660,338. Divided and thisapplication March 30, 1951, Serial No. 218,354

7 Claims. (Cl. 250'3 3.63)

This invention relates to directive antenna systems and particularly toradio lenses used in such systems.

This application is a division of my copending application Serial No.660,338, filed April 8, 1946.which matured into United States Patent2,562,277 granted July 31, 1951.

As disclosed, respectively, in Patent 2,283,935 (Figs. 16 and 17) to A.P. King and in my copending application Serial No. 642,723, filedJanuary 22, 1946, a flat cellular lens having a uniform thickness andcomprising a plurality of guides or cells, and a stepped multiplezoneplano-concave lens having a non-uniform thickness and comprising one ormore dielectric channels, have been proposed for focusing radio waves.While the uniform thickness feature of the fiat lens may be advantageousin certain systems, the focusing action of this lens is considerablyless than that of the plano-concave lens, since the flat lens does notcomprise a plurality of zones, whereas the concave lens comprisesseveral zones. Accordingly, it now appears desirable to utilize, forcertain purposes, a lens having a uniform thickness and a focusingaction fairly comparable to that obtained in the above-mentioned steppedmultiple-zone concave lens.

It is one object in this invention, in a flat lens, to obtain a greaterfocusing action than heretofore secured.

It is another object of this invention, in a line-type feed such as asectoral born, to focus the waves in the plane of the long dimension ofthe feed, in a more satisfactory manner than heretofore accomplished.

It is still another object of this invention to obtain a simple, easilyconstructed radio lens having a uniform depth or thickness.

in accordance with an embodiment of the invention, the H-plane orso-called a dimension of a single dielectric channel of uniform depth orthickness is tapered, that is, the phase velocity characteristic andhence the refractive index are tapered, for the purpose of securingfocusing action.

, In accordance with another embodiment,. an omniplanar lens having apoint focus and a uniform thickness comprises a plurality of dielectricchannels. Each channel has a tapered refractive index and the refractiveindices of corresponding portions of the channels are tapered or graded.

The invention will be more fully understood from the followingdescription of specific illustrative embodiments taken in conjunctionwith the drawing on which like reference characters denote elements ofsimilar function and in which: i

Figs. 1, 2 and 3 are perspective, front and side views, respectively, ofone embodiment of the invention comprising a dielectric channel having atapered refractive index, and Fig. 4 is a measured directive pattern forthis embodiment;

Figs. 5 and 6 are perspective and front views, respec tively, of anotherembodiment of the invention comprising a plurality of channels havingsimilarly tapered refractive indices; and

Fig. 7 is a perspective view of another embodiment of the inventioncomprising a fiat channel lens, the channels having different indicesand each channel having a tapered index.

Referring to Figs. 1, 2 and 3, reference numeral 1 denotes a sectoralhorn having a mouth aperture 2 and a throat aperture 3, and numeral 4denotes a guide connecting the throat aperture 3 to a translation device5 such as a transmitter or receiver. The horn 1 is flared in the E-plane(vertical direction), represented by the arrows 6 but not in thehorizontal direction or H-plane 7. As is universally understood by thoseskilled in the art, the E-plane of an electromagnetic wave horn orresonator or wave guide or the like, means the dimension parallel to theelectric vector of the electromagnetic wave when the device referred tois energized in the manner in which it is normally employed, or in themanner required to produce a stipulated direction of the electricvector. Likewise, the H-plane means the dimension parallel to themagnetic vector of the electromagnetic wave, for conditions of normaluse or for a specifically stipulated manner of use. The long and shortdimensions of the mouth aperture 2 are denoted by the referencecharacters I and m, respectively. Numeral 8 denotes a dielectricchannel, or lens formed in the mouth aperture 2 of the horn 1 by theinsertion of the two, doubly wedge-shaped, wall members 9 and the airdielectric medium included therebetween. The wall members 9 are eachtapered symmetrically from their respective center lines 50, 51 of Fig.1, toward both their upper and lower ends, as shown. The depth a of thechannel 8 is uniform and both faces 1%) and 11, defined as the planeswhich include the front and rear surfaces of members 9, respectively, ofthe channel 8 are plane, so that the channel constitutes a fiat lens,that is, a lens of uniform depth or thickness from its front to its rearsurfaces. As shown on the drawing, the width or a dimension of channel 8is tapered vertically in both directions from a maximum value m at themidpoint to equal minimum values n at the top and bottom extremities. Asshown, the taper is linear, i. e., it follows a straight line law ofvariation. Hence, and as explained in my copending application, SerialNo 642,723, mentioned above, the phase velocity characteristic and therefractive index of the channel are tapered. The phase velocity of thechannel 8, considered in its entirety, is greater than that of freespace; and the phase velocity increases from a minimum at the mid-pointor widest portion of the channel to a maximum at each end or the mostnarrow channel portions. in one embodiment actually constructed andtested, the dimensions 1, m, n and d, mentioned above, have values inwavelengths, M, as measured in the air of 6.76M, 0.77M, 0.56%, and1.54M, respectively, the design wavelength A being 3.4 centimeters.

In transmission, waves supplied by device 5 to guide 4 and born 1 arepropagated through the lens 8 and thence radiated. More particularly, asshown in Fig. 3, waves originating at the throat aperture 3 have acircular wave front, represented by the lines i2, in the E-plane. Sincethe phase velocity is greater at the top and bottom than at the center,the top and bottom portions of the wave front are advanced more rapidlyin phase than the central portion so that the lens 8 converts thecircular front to a linear wave front 13. In the H-plane, the front ofthe emergent wave is also substantially linear, so that the outgoingwave front is flat or plane.

Considered differently, the lens 8 functions to produce in the E-plane avery sharp beam, as shown in Fig. 4. In Fig. 4, numeral 14 denotes themajor lobe and numerals 15 denote the minor lobes of the E-plane pattern16. The major lobe is relatively sharp since its width taken at the halfpower point 17 is only 8.6 degrees. Also the minor 9} lobes are belowfifteen decibels and therefore negligible. Without the lens 8, the beamestablished by the sectoral horn would be a socalied fan-beam. With thelens 8 in position, a point type beam is established. In reception theconverse operation obtains, and the lens focuses the incoming rays onthe throat aperture 3.

Referring to Figs. 5 and 6, reference numeral 18 denotes a flatquasi-rhombic channel lens comprising a plurality of dielectric channels(5 and having a line focus 19 and an electromagnetic axis 29. Eachchannel comprises two adjacent plate members 2' 3 and the air dielectrictherebetween. The plates 241" are held in position by the wooden members2i. While the channels 8 are each electrically the as the channel 8 ofFig. l, the outer channels are bent at the center and the end or narrowchannel portions are positioned close together, so as to form a compact.structure. Numeral 22. denotes a vertically polarized line" feed orarray aligned with the focal line 19 and comprising the vertical dipoles23. The dipoles are connected by the transposed conductors Z4, 25 andthe coaxial line 26 to a translation device 5. Numeral 27 denotes .1plane reflector for the array 22.

In transmission, energy is supplied by device 5 over line 26 andconductors 25 to the dipoles 23. The dipoles are energized in phase andestablish a wave front which is circular in the E or vertical plane. inthis plane the lens 1d functions to convert the circular wave front 12to a linear front 13, whereby a high degree of directivity is secured.in reception the incoming rays are focused by the lens 13 on the lineararray 22 coincident with the focal line 19.

Referring to Fig. 7, reference numeral 63 denotes a lens having an axis69 and a focal point 70 and comprising a plurality of dielectricchannels 70, 71, 72, 73, 74, 75 and '76. Numeral '7? denotes a pointtype horn positioned at the focal point 79 and connected by the guide 73to the translating device 5. The a dimension of each channel is tapered,as in the system of Figs. 1, 5 and 6, and the indices of the severalchannels are graded as in the system of my abovementioned parentapplication, illustrated, in one specific form, by Figs. 7 and 8 of saidparent application. ln each channel the maximum refractive index is lessthan unity and the index at the center of the channel is greater thanthat at each extremity. Also, proceeding horizontally from the verticalaxial plane 78, the maximum a dimensions, and therefore the maximumrefractive indices of the channels decrease, and the values of theminimum phase velocities for the channels increase. Similarly,proceeding horizontally from the vertical axial plane 79, the minimum (5dimensions decrease and the maximum phase velocities increase; and forintermediate points in the channels above or below, and spaced at equaldistances from the horizontal axial plane 80, the a dimensions decreaseand the phase velocities increase. As in the lens of Fig. l, a taper foreach channel is selected, by the eut-and-try method. so that the desiredfocusing in the IE-plane ti is obtained and, as in the system of Figs. 7and 8 of my above-mentioned parent application, the refractive indicesof the several channels are selected so that the desired focusing in thel-l-plane 7 is secured.

The operation of the system of Fig. 7 is believed to be obvious in viewof the discussion given above in connection with Fig. l and in my parentapplication in connec tion with Figs. 7 and 8 of said application.Briefly, the horn 77 emits a spherical wave front which, by reason ofthe focusing action of lens 68 in both the H and Eplanes, is convertedto a plane wave front. In reception, the incoming rays are focused inboth planes upon the horn 77.

Numerous and varied other applications of the principles of theinvention can readily be devised, by those skilled in the art, withinthe spirit and scope of the invention. The above-described specificembodiments are illustrative only.

What is claimed is:

l. A lens for high frequency, electromagnetic waves which includes aplurality of plane sheet members having substantially uniform widths andsubstantially uniform lengths, one set of longitudinal edges of saidmembers lying in and defining a first plane surface, the other set oflongitudinal edges of said members lying in and defining a second planesurface parallel to said first plane surface and at a distance from saidfirst surface equal to the width dimension of said members, said membersbeing aligned in a row the spacing between each member and the nextadjacent member in the row being a maximum in the transverse plane whichincludes the lateral center lines of said members, said spacing beingtapered and decreasing uniformly from said transverse plane toward bothends of said adjacent members.

2. The lens of claim 1, the tapered spacings between each pair ofadjacent members being substantially equivalent.

3. The lens of claim 1, the tapered spacings between the adjacent pairsof said members differing progressively throughout at least one zone,being maximum between the central members of each zone and diminishingin both directions between adjacent successive members along the lateralaxis of the assembled lens, the spacings between the outermost membersof each zone and their respective adjacent members being of minimumaverage width in the direction of said lateral axis.

4. In an electromagnetic wave, high frequency, antenna system, thecombination which comprises a horn antenna member and an electromagneticwave lens member, said lens member being positioned to interceptelectromagnetic waves leaving or entering said horn antenna member, saidlens member comprising at least a pair of plane sheetmembers havingsubstantially identical widths and substantially identical lengths, oneset of longitudinal edges of said members lying in and defining a firstplane surface, the other set of longitudinal edges of said members lyingin and defining a second plane surface, said first and said secondsurfaces being parallel to each other and sub stantially perpendicularto the longitudinal axis of said horn member, said surfaces being spacedapart a distance equal to the common width dimension of said members,said members being spaced from each other a maximum distance in thetransverse plane which includes their lateral center lines, the spacingbetween said members decreasing uniformly from said transverse planetoward both ends of said members.

5. An electromagnetic wave, high frequency antenna comprising incombination a sectoral horn having a pair of plane parallel sides and apair of plane diverging sides and a dielectric electromagnetic lensmounted in the mouth of said horn, said lens comprising a plurality ofconductive Wedge-shaped members in the mouth of said horn restrictingthe opening thereof to a dielectric channel having a lengthsubstantially exceeding its width and a sub stantially uniform depth inthe direction of wave propagation thcrethrough, the width of saidchannel being tapered from a maximum at the center to minima at the endsof said channel.

6. An electromagnetic wave, high frequency, refractive antenna memberwhich includes a plurality of dielectric channels placed side by sidewith their longitudinal axes substantially parallel, each of saidchannels having a length substantially exceeding both its width and itsdepth, the width of each of said channels being tapered. in which themaximum width of the respective channels is decreased from channel tochannel in both directions from the centermost channel throughout atleast one group of said channels.

7. A refractor for microwave frequency, electromagnetic waves, saidrefractor comprising a wave guiding channel defined solely by twosimilar, spaced, plane, rectangular, conductive members, said channelhaving a first orifice in a first plane, said first plane including afirst longitudinal edge of each of said two conductive mem bers, saidfirst orifice comprising the space between said first longitudinaledges, said channel having a second orifice in a second plane, parallelto said first plane, said second plane including the second longitudinaledge of each of said two conductive members, said second orificecomprising the space between said second longitudinal edges, theopposing surfaces of said conductive members being perpendicular to saidfirst and second planes and approximately parallel to each other, bothsaid conductive members being bent in the vicinity of their respectivelateral center lines whereby the separation between said members is amaximum substantially between said lateral center lines and tapersgradually to similar minima between the corresponding extremities ofsaid members.

References Cited in the file of this patent UNITED STATES PATENTS2,206,683 Wolfi July 2, 1940 2,206,923 Southworth July 9, 1940 2,415,807Barrown et al. Feb. 18, 1947 2,425,488 Peterson ct al. Aug. 12, 19472,442,951 Iams June 8, 1948 2,479,673 De Vere Aug. 23,

